TGF-β and Eomes control the homeostasis of CD8+ regulatory T cells

In addition to Foxp3(+) CD4(+) regulatory T cells (CD4(+) T reg cells), Foxp3(-) CD8(+) regulatory T cells (CD8(+) T reg cells) are critical to maintain immune tolerance. However, the molecular programs that specifically control CD8(+) but not CD4(+) T reg cells are largely unknown. Here, we demonstrate that simultaneous disruption of both TGF-beta receptor and transcription factor Eomesodermin (Eomes) in T cells results in lethal autoimmunity due to a specific defect in CD8(+) but not CD4(+) T reg cells. Further, TGF-beta signal maintains the regulatory identity, while Eomes controls the follicular location of CD8(+) T reg cells. Both TGF-beta signal and Eomes coordinate to promote the homeostasis of CD8(+) T reg cells. Together, we have identified a unique molecular program designed for CD8(+) T reg cells.